get, copy, move: Display an error message when an identical transfer is already in progress, rather than failing with no indication why.

Logs/Transfer.hs

@@ -113,20 +113,25 @@ runTransfer t file shouldretry a = do
 	info <- liftIO $ startTransferInfo file
 	(meter, tfile, metervar) <- mkProgressUpdater t info
 	mode <- annexFileMode
+	fd <- liftIO $ prep tfile mode info
 	ok <- retry info metervar $
-		bracketIO (prep tfile mode info) (cleanup tfile) (a meter)
+		bracketIO (return fd) (cleanup tfile) (a meter)
 	unless ok $ recordFailedTransfer t info
 	return ok
   where
-	prep tfile mode info = catchMaybeIO $ do
-		fd <- openFd (transferLockFile tfile) ReadWrite (Just mode)
-			defaultFileFlags { trunc = True }
-		locked <- catchMaybeIO $
-			setLock fd (WriteLock, AbsoluteSeek, 0, 0)
-		when (locked == Nothing) $
-			error $ "transfer already in progress"
-		writeTransferInfoFile info tfile
-		return fd
+	prep tfile mode info = do
+		mfd <- catchMaybeIO $
+			openFd (transferLockFile tfile) ReadWrite (Just mode)
+				defaultFileFlags { trunc = True }
+		case mfd of
+			Nothing -> return mfd
+			Just fd -> do
+				locked <- catchMaybeIO $
+					setLock fd (WriteLock, AbsoluteSeek, 0, 0)
+				when (locked == Nothing) $
+					error $ "transfer already in progress"
+				void $ tryIO $ writeTransferInfoFile info tfile
+				return mfd
 	cleanup _ Nothing = noop
 	cleanup tfile (Just fd) = do
 		void $ tryIO $ removeFile tfile

debian/changelog

@@ -26,6 +26,8 @@ git-annex (4.20130315) UNRELEASED; urgency=low
   * webapp: Force wrap long filenames in transfer display.
   * assistant: The ConfigMonitor left one zombie behind each time
     it checked for changes, now fixed.
+  * get, copy, move: Display an error message when an identical transfer
+    is already in progress, rather than failing with no indication why.
 
  -- Joey Hess <joeyh@debian.org>  Fri, 15 Mar 2013 00:10:07 -0400
 

doc/bugs/Cannot_copy_to_a_git-annex_remote.mdwn

@@ -9,3 +9,6 @@ I do "git copy --to storage FILE" and it says "Copying FILE... failed".  That's
 How do I fix things so that I can copy again?  Nothing that I tried had any effect on the problem.
 
 Thanks!
+
+> Thanks to Jim's smart correlation of this with another bug, I've fixed
+> them both. [[done]] --[[Joey]]

doc/bugs/get_failed__44___but_remote_has_the_file.mdwn

@@ -33,3 +33,8 @@ Same `git annex version` on both `pilot` and `bucket`, and I ran `git annex sync
     upgrade supported from repository versions: 0 1 2
 
 How should I debug this?
+
+> [[done]], in c6fbed48 I had made some changes to allow transfers
+> to work from readonly filesystems, but a too broad error trapping
+> hid the "transfer already in progress" error it is supposed to display
+> in this case. --[[Joey]]